IDO1 and neoplasm: Three of those trials used metabolic modulators (IDO-1 inhibitors, and HDAC inhibitors), while three trials used “other” mechanisms [21,22,23] including vitamin D as a cell cycle inhibitor [24], beta blockers to limit catecholamine exposure for the tumor [25], and PV-10 as an intralesional therapy to disrupt cell lysosomes [26] (Supplementary Table S1).